Imagine a smartphone app that can see through frosted glass, the kind protecting our privacy in bathrooms, and take sharp, clear photographs. Technology that can do just that is being developed by the Applied Physics Department at Hebrew University.
Dr. Ori Katz and his colleagues in the Advanced Imaging Unit have achieved distinct photographs of images beyond semi-opaque glass using a smartphone. Voyeurs wanting to peep are likely to make the advanced optical technology a hit; grant money probably won’t be a problem, he jokes.
Katz, however, has loftier goals in mind, such as medical imaging. For instance, seeing through tissue. Not to look at the naked body but inside it; to observe what happens beneath our skin, at resolution so high it’s microscopic.
Ultrasound, CT and MRI scans do peer into our bodies, all at unsatisfactory resolution. Looking inside in detail, for instance to search for cancer cells, generally requires invasive techniques. Also, the technology would be particularly useful for brain research. Hebrew University’s Brain Sciences Department, whose building is “ten pine trees” from his lab, Katz says, is showing keen interest in their progress.
His team of students is working in several directions simultaneously; though, Katz cautions, some of the apps have a long way to go. He’s also looking for more doctoral students to join the team.
The work is based on experiments, some done by Katz in collaboration with the Weizmann Institute of Science, and by a number of teams around the world, which have collectively shaken up the conventional wisdom in physics about what happens when light passes through a semi-opaque surface, or hits a white wall.
Seeing the light
If we place a fingertip on a source of bright light, even an elevator button, we can see light through our skin. It is not opaque, Katz observes. Our skin does not block all the light, but disperses it in a manner that does not enable us to clearly see through the skin, either inside the fingertip or the elevator button.
The technologies Katz and the team are inventing are based on new advances in computerized control of photography and lasers. While about it, they discovered physical laws in places thought to have been governed by randomness.
Katz grew up in Batzra, a moshav near Ra’anana. He graduated the Israeli army’s elite Talpiot training program for technological and scientific leadership and did his doctorate at the Weizmann Institute. A year ago he returned to Israel from his post-doc in Paris.
When explaining his work, Katz doesn’t refer to seeing, but to information. Light, he says, contains information about its origin. The paradigm change his team revealed is that when light is dispersed, that information is not lost, as has historically been assumed. “It had been assumed that light scatters completely randomly,” he says. “We showed there are rules that are preserved, and using computers and cameras – which exist in every smartphone today – the shape of the object on the other side can be extracted.
How do we get from here to seeing through our skin?
A lot of challenges remain, Katz admits, a key one being that tissues have a lot more volume than a frosted bathtub door. One can, however, think of tissue as being like a series of frosted windows, one after the other, he says.
Another problem with actual living systems is that they’re complex. Living tissue does not consist of isolated components. Each cell is complex and exists next to other cells and if one uses the technology as is, Katz says, the ensuing picture is confusing.
So one issue is how to confine one’s observation to a narrow area, he explains. Right now they’re working on combining elements of ultrasound and lasers. The physics of sound may also come into play in defining narrow areas: Sound waves can be concentrated inside tissue and don’t scatter like light waves, Katz says.
Yet another challenge is that tissue, a biological living thing, constantly changes. It’s in flux. Things happen, move along. If the area under examination has blood vessels, for instance, the way the tissue scatters the light changes as a function of the blood flow.
To put things into proportion, Katz elaborates: They’re not thinking about diving centimeters under the skin, but millimeters. Even that would be a breakthrough.
The military would have its own handy applications for technology that can see around corners and through semi-opaque walls. But for the time being, Katz chuckles, the most commonly found use of laser technology is probably still hair removal.
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